Yahya related to me from Malik that Yahya ibn Said said,
"I vowed to walk, but I was struck by a pain in the kidney,
so I rode until I came to Makka. I questioned Ata ibn Abi Rabah
and others, and they said, 'You must sacrifice an animal.' When I
came to Madina I questioned the ulama there, and they ordered me
to walk again from the place from which I was unable to go on. So
I walked."

Yahya said that he had heard Malik say, "What is done
among us regarding someone who makes a vow to walk to the House of
Allah, and then cannot do it and so rides, is that he must return
and walk from the place from which he was unable to go on. If he
cannot walk, he should walk what he can and then ride, and he must
sacrifice a camel, a cow, or a sheep if that is all that he can
find."

Malik, when asked about a man who said to another, "I will
carry you to the House of Allah", answered, "If he
intended to carry him on his shoulder, by that he meant hardship
and exhaustion to himself, and he does not have to do that. Let
him walk by foot and make sacrifice. If he did not intend
anything, let him do hajj and ride, and take the man on hajj with
him. That is because he said, 'I will carry you to the house of
Allah.' If the man refuses to do hajj with him, then there is
nothing against him, and what is demanded of him is
cancelled."

Yahya said that Malik was asked whether it was enough for a man
who had made a vow that he would walk to the House of Allah a
certain (large) number of times, or who had forbidden himself from
talking to his father and brother, if he did not fulfil a certain
vow, and he had taken upon himself, by the oath, something which
he was incapable of fulfilling in his lifetime, even though he
were to try every year, to fulfil only one or a (smaller) number
of vows by Allah? Malik said, "The only satisfaction for that
that I know is fulfilling what he has obliged himself to do. Let
him walk for as long as he is able and draw near Allah the Exalted
by what he can of good."